Thank you all. Has anyone actually been there on Dec. 25, 26, 27 or 28? Those are our potential park days, although we won't be going on all of them. They all look equally busy according to the calendars.
We are there every year on those days (at least since 1999.) You will likely see at least 2 days with closures. Most likely the 26th and probably the 27th. A level one is all gates open. Level 2 they stop selling 1 day tickets, level 3 they stop selling everything except APs. Level 4 they stop allowing new tickets. Level 5, all entry is ceased (well, almost all, VIP guided tours have full access.) And if you have dining reservations, they will not charge you the $10 per person for missing it as they will not let you in. (Exception is Club 33, they will escort you in.)
Generally, closures only last until after the 1st parade, when people generally exit to nap. The fire marshal will then lift the closure, and the front gate managers will start bringing the levels back down. If they are expecting a possible closure, you might notice green taped switchbacks in the esplanade.
Expect ride times to be 90 mins to 2 hours. Try to eat at off peak times. Don't expect to walk up and get seating at sit down restaurants, you will usually get "We aren't taking walk ups today." Take your patience with you. Follow CMs directions for paths. Too often people will want to go against traffic, and all that does is slow everyone down. It will be VERY crowded. One day of those days last year, it was so crowded, it took us 30 mins to get from Haunted Mansion to the bridge at Pirates.
October was very busy. But it wasn't as busy as the 26th and 27th will be.
Unless it rains, then while it will still be busy, it won't be as bad.